Processes to convert renewable resources into transportation fuels usually involve several steps. For example, one approach is to use acids to convert carbohydrates, starches, lignins, and other biomass into sugars such as glucose, lactose, fructose, sucrose, dextrose. Another approach is to convert biomass solids and liquids into pyrolysis oil.
Pyrolysis is the chemical decomposition of organic materials by heating in the absence of oxygen or other reagents. Pyrolysis can be used to convert biomass (such as lignocellulosic biomass) into pyrolysis oil or so-called bio-oil, a liquid product made by heating biomass to high temperatures (typically 350-500° C.) under inert atmosphere with a short residence time. The pyrolysis oil liquid contains molecules derived from the original cellulose, hemicellulose, and lignin in the biomass feedstock, and is consequently a mixture of primarily oxygenated products. Pyrolysis oil typically is thermally unstable, acidic, and not miscible with petroleum feedstocks. The components in the pyrolysis oil that were derived from the hemicellulose and cellulosic components in the biomass are composed of C5-C6 or lower carbon chain polyols and oligomers thereof.
Cortright, et al., US20080300435, uses processes and reactor systems for the conversion of oxygenated hydrocarbons to hydrocarbons, ketones and alcohols useful as liquid fuels, such as gasoline, jet fuel or diesel fuel and industrial chemicals. Cortright, et al., U.S. Pat. No. 6,953,873, describes a method of producing hydrocarbons from oxygenated hydrocarbon reactants, such as glycerol, glucose, or sorbitol. Marker, et al., US20080053870, uses a process for the conversion of biomass to a liquid fuel including the production of diesel and naphtha boiling point range fuels by hydrocracking of pyrolysis lignin extracted from biomass. Corma, et al., (2007) studied the catalytic cracking of glycerol and sorbitol, as representative of biomass-derived oxygenates, at 500-700° C. with six different catalysts, including a fresh fluid catalytic cracking (FCC) catalyst (FCCl), an equilibrium FCC catalyst with metal impurities (ECat), a mesoporous Al2O3, a USY zeolite (Y), a ZSM5-based FCC additive (ZSM5), and an inert silicon carbide (SiC).
Unfortunately, bio-oils produced from biomasses are a chemically complex mixture of compounds comprising generally a mixture of water, light volatiles, and non-volatiles. As a fuel, bio-oil has a number of negative properties such as high acidity (corrosiveness), substantial water content (usually in the range of 15% to 30%), it is not miscible with hydrocarbon fuels, variable viscosity, low heating values (about half that of a typical diesel fuel), high oxygen content and low cetane number. These negative properties are related to the oxygenated compounds contained in bio-oils that result in a 45 wt % oxygen content. Therefore, it is necessary to upgrade the raw bio-oils before they can be used as a viable renewable fuel.
Currently, there are no commercial technologies that will allow the production of fungible renewable fuels from bio-oil. Technologies need to be developed that can generate sufficient renewable fuel volumes to replace current non-renewable fuel sources. Therefore, new methods and processes for upgrading bio-oils obtained by pyrolysis of biomass or waste to thermally stable and fungible renewable fuels are required.